Fas agonist antibody CH11 enhances apoptosis in sulfur mustard‐exposed human keratinocytes and airway epithelial cells

Abstract

Sulfur mustard (SM, bis-(2-chloroethyl) sulfide), known as mustard gas, causes debilitating skin blisters and injuries to the eyes and the respiratory tract; these being attributed to SM-induced epithelial damage, mainly basal cell apoptosis. Previous studies have shown that SM induced apoptosis is mainly mediated by caspases 8 (death receptor pathway) and 9 (mitochondrial pathway); however, which member of the TNF super family is the major activator of caspase 8 remains unknown. We used monoclonal agonist (CH11) and antagonist (ZB4) antibodies that are selective for the Fas receptor to elucidate the role of Fas in SM-induced apoptosis in cultured human epidermal keratinocytes (NHEK, skin model), human bronchial/tracheal epithelial cells (NHBE, upper lung model), and small airway epithelial cells (SAEC, deep lung model). Activation of the Fas pathway was evaluated by measuring the activation of the executioner caspase 3 by fluorogenic caspase substrate hydrolysis assay. We found that CH11 was able to significantly increase caspase 3 activation in all three cell types ± SM. The activation of caspase 3 was amplified when CH11 was given in conjunction with SM, this effect was maximal at the EC50 of SM (98 μM NHBE; 208 μM SAEC; 223 μM NHEK). ZB4 was able to attenuate the caspase 3 activation induced by SM and CH11. These results suggest that the Fas receptor has a role in the activation of caspase 3 due to SM.